Background

In recent years, ‘Get It Right First Time (GIRFT)’ have advocated cemented replacements in femoral part of Total hip arthroplasty (THA) especially in older patients. However, many studies were unable to show any difference in outcomes and although cemented prostheses may be associated with better short-term pain outcomes there is no clear advantage in the longer term. It is not clear when and why to do cemented instead of cementless.

The significance of ring-fencing orthopaedic beds and protected elective sites have recently been highlighted by the British Orthopaedic Association & Royal College of Surgeons. During the pandemic many such elective setups were established with various degrees of success. This study aimed to compare the functioning and efficiency of a Orthopaedic Protected Elective Surgical Unit (PESU) instituted during the pandemic with the pre-pandemic elective service at our hospital (Pre-Pandemic ward or PPW).

We retrospectively collected data of all patients who underwent elective Orthopaedic procedures in a protected elective unit during the pandemic (March 2020 – July 2020) and a similar cohort of patients operated via the routine elective service immediately prior to the pandemic (October 2019 – February 2020). Various parameters were compared and analysed. To minimise the effect of confounding factors a secondary analysis was undertaken comparing total hip replacements (THR) by a single surgeon via PESU (PESU-THR) and PPW (PPW-THR) over 5 months each from March-July 2021 and March-July 2019 respectively.

A total of 192 cases were listed on PESU during the studied period whereas this number was 339 for PPW. However more than half (52%) of those listed for a surgery on PPW were cancelled and only 162 cases (48%) were actually performed. PESU had a significantly better conversion rate with only 12.5% being cancelled and 168 (87.5%) cases performed. 49% (87 out of 177) of the cases cancelled on PPW were due to a ‘bed unavailability’. A further 17% (30/177) and 16% (28/177) were cancelled due to ‘emergency case prioritisation’ and ‘patient deemed unfit’ respectively. In contrast only 3 out of the 24 patients cancelled on PESU were due to bed unavailability and the main reason for cancellation here was ‘patient deemed unfit’ (9/24). Single surgeon THR, showed similar demographic features for the 25 patients on PESU and 37 patients on PPW. The average age for these patients was 63 on PESU and 69 on PPW whereas the BMI was 33 and 30 respectively. The patients on PESU also demonstrated a decrease in length of hospital stay with an average of 3 days in comparison to 4.8 days for those admitted to PPW. PROMS scores were comparable at 6 weeks with an average improvement of 16.4/48 in the PESU-THR cohort and of 18.8/48 in the PPW-THR cohort. There were no readmissions or revisions recorded in the PESU-THR cohort while the PPW-THR cohort had 1 readmission and revision.

Our study shows how a small ring fenced Orthopaedic elective unit in a district general hospital, even during a global pandemic, can function more efficiently than a routine elective facility with many shared services.

There is growing interest in the peri-operative management of patients with indications for hip and knee arthroplasty in the setting of modifiable risk factors such as morbid obesity, type 2 diabetes mellitus, and smoking. A recent survey of the American Association of Hip and Knee Surgeons (AAHKS) found that 95% of respondents address modifiable risk factors prior to surgery. The aim of this study was to poll Australian arthroplasty surgeons regarding their approach to patients with modifiable risk factors.

The survey tool used in the AAHKS study was adapted for use in the Australian context and distributed to the membership of the Arthroplasty Society of Australia via Survey Monkey.

Seventy-seven survey responses were received, representing a response rate of 64%. The majority of respondents were experienced, high volume arthroplasty surgeons. Overall, 91% of respondents restricted access to arthroplasty for patients with modifiable risk factors. Seventy-two percent of surgeons restricted access for excessive body mass index, 85% for poor diabetic control, and 46% for smoking. Most respondents made decisions based on personal experience or literature review rather than hospital or departmental pressures.

Despite differences in healthcare systems, our findings were similar to those of the AAHKS survey, although their responses were more restrictive in all domains. Differences were noted in responses concerning financial considerations for potentially underprivileged populations. The survey is currently being administered by arthroplasty societies in six other countries, allowing comparison of orthopaedic practice across different healthcare systems around the world.

In conclusion, over 90% of Australian arthroplasty surgeons who responded to the survey address modifiable risk factors prior to surgery.

Deep infection is a devastating complication of total knee arthroplasty (TKA). This study aimed to determine if there was a relationship between surgeon volume and the incidence of revision for infection after primary TKA.

Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) from 1 September 1999 to 31 December 2020 for primary TKA for osteoarthritis that were revised for infection. Surgeon volume was defined by the number of primary TKA procedures performed by the surgeon in the year the primary TKA was performed and grouped as <25, 25-49, 50-74, 75-99, >100 primary TKA procedures per year. Kaplan Meir estimates for cumulative percent revision (CPR) and Cox Proportional Hazard Ratios were performed to compare rates of revision for infection by surgeon volume, with sub-analyses for patella and polyethylene use, age <65 years and male gender.

5295 of 602,919 primary TKA for osteoarthritis were revised for infection. High volume surgeons (>100 TKA/year) had a significantly lower rate of revision for infection with a CPR at 1 and 17 years of 0.4% (95% CI 0.3, 0.4) and 1.5% (95% CI 1.2, 2.0), respectively, compared with 0.6% (95% CI 0.5, 0.7) and 2.1% (95% CI 1.8, 2.3), respectively, for low volume surgeons (<25 TKR/year). Differences between the high-volume group and the remaining groups remained when sub-analysis for age, gender, ASA, BMI, patella resurfacing and the use of cross-linked polyethylene (XLPE).

High volume surgeons have lower rates of revision for infection in primary TKA.

Strategy regarding patella resurfacing in total knee replacement (TKR) remains controversial. TKR revision rates are reportedly influenced by surgeon procedure volume. The study aim was to compare revision outcomes of TKR with and without patella resurfacing in different surgeon volume groups using data from the AOANJRR.

The study population included 571,149 primary TKRs for osteoarthritis. Surgeons were classified as low, medium, or high-volume based on the quartiles of mean primary TKR volume between 2011 and 2020. Cumulative percent revision (CPR) using Kaplan-Meier estimates of survivorship were calculated for the three surgeon volume groups with and without patella resurfacing. Cox proportional hazards models, adjusted for age and sex, were used to compare revision risks.

High-volume surgeons who did not resurface the patella had the highest all-cause CPR (20-year CPR 10.9%, 95% CI [10.0%, 12.0%]). When the patella was resurfaced, high-volume surgeons had the lowest revision rate (7.3%, 95% CI [6.4%, 8.4%]). When the high-volume groups were compared there was a higher rate of revision for the non-resurfaced group after 6 months. When the medium-volume surgeon groups were compared, not resurfacing the patella also was associated with a higher rate of revision after 3 months. The low-volume comparisons showed an initial higher rate of revision with patella resurfacing, but there was no difference after 3 months. When only patella revisions were considered, there were higher rates of revision in all three volume groups where the patella was not resurfaced.

TKR performed by high and medium-volume surgeons without patella resurfacing had higher revision rates compared to when the patella was resurfaced. Resurfacing the patella in the primary procedure protected against revision for patella reasons in all surgeon volume groups.

Level of evidence: III (National registry analysis)

‘Getting It Right First Time’ guidance recommends the universal use of cemented prostheses in patients aged over 65 within the UK. This cut off has since been raised to 70. The report claims that the increased cost of uncemented technology is not justifiable in terms of patient outcomes. Our aim was to evaluate any disparity between patients across these age thresholds, in terms of functional outcomes, complication and costs following elective uncemented THR.

We utilised a single surgeon prospectively updated database, to compare functional outcome of patients aged over and under 65 and again at 70 following elective uncemented THR. We measured functional outcome using Oxford Hip Score (OHS). Patients were followed routinely for up to 2 years and subsequently up to 6 years.

Patient ages ranged from 23–89. Over 97% of patients reported an improvement in hip function, with an average increase of 24.1 in OHS. There was no statistical significance between patient age and functional hip outcome, p=0.108 with a cut off at 65 and p=0229 at 70. 1.1% of under 65s required revision surgery, compared to 2.3% of over 65s. 1.4% of patients under 70 required revision surgery, compared to 2.5% in those above. The most common reason for revision surgery was debridement, antibiotics and implant retention. Patients under 65 had a 1.4% chance of experiencing a fracture or dislocation, compared to 2.5% of patients over 65. 2.0% of patients under 70 experienced a fracture or dislocation, in comparison to 2.2% in those over 70. There was 1 recorded mortality, a patient aged over 70. Cost analysis is challenging accounting for all variables between techniques. Cementing invariably requires additional operating time and diminished theatre efficiency, with direct cost estimated at £364 in theatre running fees per case.

Within the series, uncemented THRs was found to be a safe and efficacious procedure irrespective of age. Functional hip outcome was not correlated to patient age, conflicting with GIRFT recommendations. The extra duration of cemented surgery may equilibrate the financial disparity of uncemented practice.

Tibial cut is a crucial step in ensuring adequate and appropriate proximal tibial resection for mechanical orientation and axis in total knee replacement. We evolved the concept and technique of Condylar Differential for planned tibial cuts in conventional total knee replacement, which accounts for individual variations and reflects individual mechanical orientation and alignment.

We used Condylar Differential in 37 consecutive total knee replacements including valgus knees and severe advanced osteoarthritis. First a vertical line is drawn on digital weight bearing anteroposterior radiograph for mechanical axis of tibia. Then a horizontal line is drawn across and perpendicular to the mechanical axis. The distances between the horizontal line and the lowest reproducible points of articular surfaces of medial and lateral tibial condyles respectively are measured. The difference between two measurements obviously represents Condylar Differential. Condylar Differential, adjusted to the nearest millimetre, is maintained in executing tibial cuts, successively if necessary.

Condylar Differential measurement showed a very wide variation, ranging from 8–6 (2 mm) to 10-0 (10 mm). We found that prior measurement of Condylar Differential is a simple, consistent and effective estimate and individualises the tibial cut for optimal templating of tibia. We encountered no problems, adopting this technique, in our series.

Condylar Differential contributes to optimal individualised tibial cut in conventional total knee replacement and is a useful alternative to computer navigated option with comparable accuracy in this respect. While we used the technique in digitised radiographs, this technique can also be applied to plain films, allowing for magnification.

DAIR procedure is well established for Prosthetic Joint Infection (PJI) in acute setting after total hip and knee replacements. We present our experience of DAIR following hip and knee replacements in a District General Hospital (DGH), where we delivered comparable results to leading tertiary centres in short to mid-term followup.

We undertook a retrospective study involving 14 patients, who underwent DAIR in our DGH between August 2012 and December 2015. Patient cohort included primary, complex primary and revision hip and knee replacements. Microbiological support was provided by a Microbiologist with interest in musculoskeletal infections.

14 patients [9 males, 5 females; age 62 to 78 years (Mean 70.7); BMI 22 to 44.2 (Mean 33.8)] with multiple comorbidities underwent DAIR procedure within 3 weeks of onset of symptoms. 12 out of 14 grew positive cultures with two growing Vancomycin resistant Enterococci. Intravenous antibiotics were started after multiple samples intraoperatively and continued in six patients after discharge, while 8 were discharged with oral antibiotics. One patient died of overwhelming intraoperative septic shock in postoperative period. Another patient died of myocardial infarction subsequently. 12 (85.7%) patients were doing well with regular followup (Mean 20 months).

With good patient selection, DAIR is a far simpler solution and a safe and reproducible surgical option for early PJI following hip and knee replacements compared to one or two stage revisions. But published data in contemporary literature is predominantly from specialised centres. Our small series provides a perspective of comparable early to mid-term results of DAIR from DGH.

Background

Mechanics and kinematics of the knee following total knee replacement are related to the mechanics and kinematics of the normal knee. Restoration of neutral alignment is an important factor affecting the long-term results of total knee replacement. Tibial cut is a vital and crucial step in ensuring adequate and appropriate proximal tibial resection, which is essential for mechanical orientation and axis in total knee replacement. Tibial cut must be individually reliable, reproducible, consistent and an accurate predictor of individual anatomical measurements. Conventional tibial cuts of tibia with fixed measurements cannot account for individual variations. While computer navigated total knee replacement serves as a medium to achieve this objective, the technology is not universally applicable for differing reasons. Therefore we evolved the concept and technique of Condylar Differential for planned tibial cuts in conventional total knee replacement, which accounts for individual variations and reflects the individual mechanical orientation and alignment.

OBJECTIVE

Debridement, Antibiotics and Implant Retention (DAIR) procedure is well established for Prosthetic Joint Infection (PJI) in acute setting after total hip and knee replacements. We present our perspective of DAIR in a relatively a small cohort following hip and knee replacements in a District General Hospital (DGH) in United Kingdom, where we delivered comparable results to leading tertiary centers in short to mid-term followup.

Aims

Displaced femoral neck fractures (FNF) may be treated with partial (hemiarthroplasty, HA) or total hip arthroplasty (THA), with recent recommendations advising that THA be used in community-ambulant patients. This study aims to determine the association between the proportion of FNF treated with THA and year of surgery, day of the week, surgeon practice, and private versus public hospitals, adjusting for known confounders.

Debridement Antibiotics Implant Retention (DAIR) is a recognised procedure in the management of acute prosthetic joint infection (PJI). We present an experience of DAIR following hip and knee replacements in a District General Hospital.

A retrospective review of 14 patients who underwent DAIR procedures between August 2012 and December 1015 were collated. The cohort included primary, complex primary and revision hip and knee replacements. All patients received multidisciplinary care with surgery performed by one of two arthroplasty surgeons.

9 males and 5 females with age 62 − 78 years (Mean 70.7) and BMI 22–44.2 (Mean 33.8) with various co-morbidities underwent DAIR. Surgical criteria required DAIR to be performed within 3 weeks of the onset of symptoms of infection. The time from index surgery however ranged from 15 days to 58 months. 12 of 14 grew positive cultures including two growing Vancomycin Resistant Enterococcus. Intravenous antibiotics were commenced after intraoperative samples and tailored OPAT. Antibiotic schedule varied from six weeks to eight months. 12 (85.7%) patients remain under follow up. Mean follow is 20 months (RANGE 6months-3years10months) with no recurrence of infection or reoperation.

With appropriate patient selection, DAIR is safe and reproducible surgical option in PJI in hip and knee replacements, avoiding the implications of a one or two stage revision. Published Data in contemporary literature is predominantly from specialised centres. Our small series provides a perspective of early to mid term results of DAIR to DGH. Interestingly each procedure is categorised as a failed implant on the National Joint Register.

Aims

The aim of this consensus was to develop a definition of post-operative fibrosis of the knee.

Introduction:

One method of femoral head preservation following avascular necrosis (AVN) is core decompression and Tantalum Rod insertion. There is, however, a published failure rate of up to 32% at 4 years. The purpose of the present study was to document the clinical and radiological outcome following Total Hip Arthroplasty (THA) subsequent to failed Tantalum Rod insertion.

Background

Ultrasound and MRI are recommended tools in evaluating postoperative pain in metal-on-metal hip (MoM) arthroplasty.

The modern generation of hip resurfacing arthroplasties was developed in the early 1990's with one of the original designs being the McMinn Resurfacing Total Hip System. This was a hybrid metal on metal prosthesis, with a smooth hydroxyapetite coated press fit mono block cobalt chrome shell with a cemented femoral component. Although no longer produced in this form, lessons may be learned from this original series of components. With metal on metal resurfacing arthroplasty now facing criticisms and concerns with regard function, bone preservation capability and soft tissue issues such as ‘pseudotumors’, it is the aim of this long-term study to assess the outcome and survival of an original series of resurfacing arthroplasties.

27 resurfacing arthroplasties were performed in 25 consecutive patients between June 1994 and November 1996. 16 right hips and 11 left were performed in 14 female patients and 11 male patients. The average age at the time of surgery was 50.5 years (SD 7.9, range 30-63). All surgeries were performed by a single surgeon using a posterior lateral approach. Following the initial early care, each patient received bi-annual follow up along with open access to the clinic with any concerns or complications. A retrospective review of the case notes was conducted and outcome scores retrieved from a prospectively updated database. Radiographs were analyzed and a Kaplan Meier survival chart was constructed for the group.

At latest review 3 patients have died (5yrs, 8yrs and 13.8yrs) and 1 patient has been lost to follow up (5yrs). 7 resurfacings have required revision, all due to acetabular loosening, at a mean follow up of 7 years 11months (SD 2.03years, range 4-10). Metallosis was documented in 4 of the revision cases, however no extensive soft tissue inflammation or ‘pseudotumor’ identified. The mean follow up of the remaining 16 hips is 12years and 10months (SD 12.8months, Range 10.4yrs-14.0 years). The Kaplan Meier survival at a minimum follow up of 10 years is 75.8% (95% CI 0.67-0.95). Mean Oxford hip scores at latest follow up was 20.6 (SD 8.8, range 12-38). There was no significant difference between cup inclination angles for the surviving cohort and those who required a revision procedure with mean cup inclinations of 52.5 (SD 5.5, range 45-60) and 58 degrees respectively (SD 9.1, range 50-70)(p=0.255).

This original series of hip resurfacings, with up to 14 years follow up, shows a survival of 76% at the minimum follow up of 10 years. All failures were due to loosening of the smooth backed acetabulum, which with a modern porous coating, failure may have been avoided or delayed. Despite high inclinations angles no soft tissue reactions were identified within this series. No femoral failures were identified suggesting unlike much literature focus, long-term failure may not be related to the femoral head or neck.

It has been shown that a cognitive function (CF) loss can occur after hip or knee arthroplasty procedures, with an incidence of 40 to 70%. The pathogenesis remains unclear but studies suggest some form of brain emboli; although both trans-cranial doppler and trans-oesophageal doppler have both shown emboli per-operatively a correlation has never been shown with CF loss post-operatively. In contrast, in the cardiothoracic literature an embolic cause is widely accepted for detectable post-operative CF drop. The purpose of this study was to ascertain whether MRI could show evidence of embolic phenomena in patients undergoing hip or knee arthroplasty.

Twenty-five patients presenting for hip or knee arthroplasty procedures were consented for this study. Brain MRI scans and MR angiograms were performed 1 week pre-operatively and within 1 week post-operatively using a Phillips 1.5Tesla MRI unit. All scans recorded were independently reviewed by 2 radiologists. A series of tests to examine several modes of cognitive function were carried out by a clinical psychologist pre-operatively, and at 1 week post-operatively. The CF tests showed a clinically significant drop following surgery in 64% of cases – this is in keeping with other recently published data.

None of the post-operative scans or angiograms showed overt evidence of new lesions. Three Scans had equivocal tiny brainstem hypodensities on a single slice with no correlating abnormality on diffusion images to support the presence of new ischaemia.

We conclude that either the aetiology of post-operative CF drop following arthroplasty is not embolic in nature, or that with current technology MRI brain scans even with angiograms are not sensitive enough to show the corresponding abnormality. With currently available equipment there appears to be no benefit from using MRI as a tool to evaluate post-operative CF loss in this group of patients.

Oxidized Zirconium (Oxinium, Smith & Nephew, Inc., Memphis, TN) is a relatively new material that features an oxidized ceramic surface chemically bonded to a tough metallic substrate. This material has demonstrated the reduced polyethylene wear characteristics of a ceramic, without the increased risk of implant fracture. The purpose of the current investigation was to assess clinical outcomes following primary total hip arthroplasty with Oxinium versus Cobalt Chrome femoral heads.

One hundred uncemented primary total hip arthroplasty procedures were prospectively performed in 100 patients. There were 52 males and 48 females with mean age at the time of surgery of 51 years (SD 11, range, 19–76). Using a process of sealed envelope randomization, patients were divided into 2 groups. Each group contained fifty patients. Those in group 1 received an Oxinium femoral head (OX), while those in group 2 a cobalt-chrome femoral head (CC).

The current study reports clinical outcome measures for both the OX and CC groups at a minimum follow-up of 2 years postoperatively. At the time of latest follow-up, stem survival for both groups was 98%. There was a significant improvement in all clinical outcome scores between preoperative and 2 year postoperative time periods for both bearing groups (p< 0.003). There were no significant differences between bearing groups for any of the clinical outcome scores at final follow-up (p> 0.159). Mean Harris Hip Scores at 2 years postoperatively were 92 and 92.5 for OX and CC, respectively (range; 65–100 OX, 60–100 CC). For SF-12, both the Physical Component Summary Scale (PCS) and the Mental Component Summary Scale (MCS) are reported. Mean PCS scores at final follow-up were 45.2 and 49.21 for OX and CC (range; 27.1–56.7 OX, 26.3–61.8 CC). Mean MCS scores were 53.8 and 52.57 for OX and CC (range; 39.2–65.5 OX, 34.3–64 CC). Mean final WOMAC scores are reported as 84.9 and 87 for OX and CC, respectively.

The current data suggest that total hip arthroplasty utilizing Oxinium femoral heads is safe and effective. Additional follow-up of the current cohort will be performed in order to fully assess mid-to long-term clinical outcomes.

Purpose: The use of UHMW polyethylene acetabular liners is known to cause polyethylene wear related osteolysis, the major limiting factor in its use in the younger active patient. Modern alumina ceramic articulations have been developed in order to reduce wear and avoid polyethylene debris. This prospective randomized long-term study aims to compare the outcome between an alumina ceramic-on-ceramic (CC) articulation with a ceramic on UHMW polyethylene articulation (CP).

Method: Fixty-six hips in 55 patients with mean age 42.2 (range 19–56) each received uncemented components (Wright Medical) and a 28mm alumina head with acetabular liner selected via sealed envelope randomization following anesthetic induction. Subsequent regular clinical and radiologic follow up measured patient outcome scores and noted any radiological changes.

Results: Twenty-six CP hips and 30 CC hips were evaluated. One failure required revision in each group. Mean St Michael’s outcome score for each group with up to 10 years follow-up (median 8 years, range 1–10) was 22.8 and 22.9 respectively (p=0.057). Radiographs with a minimum 5 years post-operative follow-up were analyzed in 42 hips (23 CC and 19 CP). The mean time of wear measurement for the CC group was 8.3 years (SD 1.3, Range 4.8–10.1 years) and for the CP group was 8.1 years (SD 0.9, Range 6.1–9.2 years)(p=0.471). Wear was identified in all but one CP hip but in only 12 of 23 CC replacements. Mean wear in the CP group was 0.11mm per year and 0.02mm per year in the CC group (p< 0.001).

Conclusion: To our knowledge this is the first long term randomized trial comparing in-vivo ceramic-on-ceramic with ceramic-on-polyethylene hip articulations. Other than significantly greater wear in the polyethylene group there was no significant difference in long-term outcome scores between the two groups with up to 10 years of follow-up. The use of a ceramic-on-ceramic bearing is a safe and durable option in the young patient avoiding the concerns of active metal ions and osteolytic polyethylene debris.

Purpose: While the durability of most uncemented femoral stems remains unknown, it is the aim of this study to demonstrate Echelon Primary femoral stem performance with regard patient outcome and overall implant survival.

Method: Between February 1998 and March 2007, 428 patients received the Echelon Primary stem. The mean age of each patient was 58.1 (SD 11.1, Range 20–87). Body mass index averaged 30.5 kg/m2 (SD 5.8, Range 17.7–58.2). The majority of patients received a Reflection uncemented acetabular component (91%) and an ultra high molecular weight polyethylene liner (76.5%), although the highly cross linked polyethylene is now used with increased frequency, used in 31% of hips since 2005. The majority of femoral heads were cobalt chrome (79.3%).

Results: Kaplan Meier survivorship for the Echelon Femoral stem with revision for aseptic loosening as end point at 100 months is 99.3% (95% CI 97.1–99.8). Taking revision for any reason as the end point the Kaplan Meier survivorship is 98.3% at 100 months (95% CI 95.9–99.3). A pre-operative WOMAC score was available for 345 of the 392 patients with mean score of 43.5 (95% CI 41.6–45.4). At the three-month post-operative review the mean WOMAC score was significantly increased to 74.54 (95% CI 72.7–76.3)(p< 0.001) and by 1 year 84.3 (95% CI 80.5–88.1). At subsequent years, the modified WOMAC score remained at a plateau of around 80. General health assessment using the SF-36 shows an improvement in the physical component score from 33.1 (95% CI 32.3–33.9) preoperatively to 42.6 (95% CI 41.7–43.6)(p< 0.001) at three months and 48.19 (95% CI 44.2–52.2) at latest follow up. The mental component scores increased from 48.7 (95% CI 47.6–49.9) to 51.4 (95% CI 50.3–52.4)(p< 0.001) and 53.5 (95% CI 50.3–56.6) respectively.

Conclusion: This large prospective review of the Echelon Primary femoral stems reveals an excellent survivorship of the stem with a 99.3% survival at 8 years with regard aseptic loosening and 98.3% survival including revision for any reason. Patient outcome scores are significantly improved and subsequently maintained. There have been no changes with regard to manufacture or design of the stem within the period of review.