Introduction

A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). During DS, the hip flexion angle approximates the functional range of hip motion. In some hip morphologies this femoroacetabular conflict has been shown to occur as early as 80° of hip flexion. So far in-vivo HJRF measurements have been limited to instrumented hip implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). Clearly, young adults have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since hip loading data on this subgroup of the population is lacking and performing invasive measurements would be unfeasible, this study aimed to report a personalised numerical model solution based on inverse dynamics to calculate realistic in silico HJRF values during DS.

Introduction

A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). As a closed chain exercise, it has great value in rehabilitation and muscle strengthening of hip and knee. During DS, the hip flexion angle approximates the functional range of hip motion risking femoroacetabular impingement in some morphologies. In-vivo HJRF measurements have been limited to instrumented implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). On the other hand, total hip arthroplasty is being increasingly performed in a younger and higher demanding patient population. These patients clearly have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since measurements of HJRF with instrumented prostheses in healthy subjects would be ethically unfeasible, this study aims to report a personalised numerical solution based on inverse dynamics to calculate realistic in-silico HJRF values during DS.

The aim of this review is to evaluate the current available literature evidencing on peri-articular hip endoscopy (the third compartment). A comprehensive approach has been set on reports dealing with endoscopic surgery for recalcitrant trochanteric bursitis, snapping hip (or coxa-saltans; external and internal), gluteus medius and minimus tears and endoscopy (or arthroscopy) after total hip arthroplasty. This information can be used to trigger further research, innovation and education in extra-articular hip endoscopy.

The aim of this study was to determine the accuracy of registration and the precision of the resection volume in navigated hip arthroscopy for cam-type femoroacetabular impingement, using imageless and image-based registration. A virtual cam lesion was defined in 12 paired cadaver hips and randomly assigned to either imageless or image-based (three-dimensional (3D) fluoroscopy) navigated arthroscopic head–neck osteochondroplasty. The accuracy of patient–image registration for both protocols was evaluated and post-operative imaging was performed to evaluate the accuracy of the surgical resection. We found that the estimated accuracy of imageless registration in the arthroscopic setting was poor, with a mean error of 5.6 mm (standard deviation (sd) 4.08; 95% confidence interval (CI) 4.14 to 7.19). Because of the significant mismatch between the actual position of the probe during surgery and the position of that probe as displayed on the navigation platform screen, navigated femoral osteochondroplasty was physically impossible. The estimated accuracy of image-based registration by means of 3D fluoroscopy had a mean error of 0.8 mm (sd 0.51; 95% CI 0.56 to 0.94). In terms of the volume of bony resection, a mean of 17% (sd 11; -6% to 28%) more bone was resected than with the virtual plan (p = 0.02). The resection was a mean of 1 mm deeper (sd 0.7; -0.3 to 1.6) larger than on the original virtual plan (p = 0.02).

In conclusion, given the limited femoral surface that can be reached and digitised during arthroscopy of the hip, imageless registration is inaccurate and does not allow for reliable surgical navigation. However, image-based registration does acceptably allow for guided femoral osteochondroplasty in the arthroscopic management of femoroacetabular impingement.

We examined the relationships between the serum levels of chromium and cobalt ions and the inclination angle of the acetabular component and the level of activity in 214 patients implanted with a metal-on-metal resurfacing hip replacement. Each patient had a single resurfacing and no other metal in their body. All serum measurements were performed at a minimum of one year after operation. The inclination of the acetabular component was considered to be steep if the abduction angle was greater than 55°.

There were significantly higher levels of metal ions in patients with steeply-inclined components (p = 0.002 for chromium, p = 0.003 for cobalt), but no correlation was found between the level of activity and the concentration of metal ions. A highly significant (p < 0.001) correlation with the arc of cover was found. Arcs of cover of less than 10 mm were correlated with a greater risk of high concentrations of serum metal ions. The arc of coverage was also related to the design of the component and to size as well as to the abduction angle of the acetabular component. Steeply-inclined acetabular components, with abduction angles greater than 55°, combined with a small size of component are likely to give rise to higher serum levels of cobalt and chromium ions. This is probably due to a greater risk of edge-loading.

Dislocation rates after total hip arthroplasty vary from 1% to 8% and approximately 1% will require revision surgery to treat hip instability. From these revisions only 60% is successful with redislocation frequencies from 8.2% to 39%. A full-constrained acetabular cup can be used by hip surgeons as a measure of salvage. The purpose of this paper is to describe the complications the authors have encountered in a short postoperative period with the use of three different types of full-constrained acetabular cups.

Over a period of three years, between January 1999 and December 2001, 25 full-constrained acetabular components were implanted. Three different types of full-constrained prostheses were used: the Osteonics Bipolar Constrained Insert (Osteonics Corp., Allendale, NJ), the Ringloc Constrained Liner (Biomet Inc., Warsaw, IN) and the Trilogy Constrained Liner (Zimmer Inc., Warsaw, IN). In 14 cases the full-constrained cups were used in revision hip arthroplasty and in 4 cases as revision for failed full-constrained implants. Seven patients received a primary constrained acetabular prosthesis.

Of the 23 patients one woman died after a follow-up period of 25.5 months. The other 22 patients had an average clinical follow-up of 22.5 months, ranging from 16 to 47.5 months. In 8 prostheses 6 different postoperative problems were encounterd, resulting in a total of 32 % failures. Seven of the complications were different types of constrained acetabular cup disassembly and one complication was due to a failure at the interface between bone and the porous-metal surface. As alternative treatment option, the authors have used the Birmingham Hip Resurfacing (Midland Medical Technologies, Birmingham) Dysplasia cup with modular head in seven patients who sustained recurrent dislocations after multiple revision surgery, with only one failure (1/7 - recurrent dislocation) after a mean follow-up of two years.

In view of the high short-term complication rate (32%) in a follow-up period of three years, the authors strongly recommend judicious use of the constrained acetabular prosthesis. The component should only be applied as a salvage tool in selected patients in whom no other treatment options would be successful. In these cases the use of a constrained acetabular prosthesis might solve the problems encountered in the majority of patients, but it can never guarantee a problem-free course of this cup. Alternative options such as the use of large diameter femoral heads with a resurfacing cup, using a metal-on-metal friction couple should be considered as a worthwhile alternative in those cases.

Postoperative dislocations are known to be a big problem in revision surgery. In literature dislocation rates vary from 4.8% to 33% after previous surgery. In revision surgery, impingement of the implant components, the capsular and soft tissue release, muscular weakness and greater trochanter problems can give additional instability. The reason for revision is important, where instability, infection and tumour cases will lead to a higher percentage of dislocations. The use of big metal heads on polyethylene should be avoided because of the higher volumetric wear. With the new developments of metal-on-metal hip resurfacing and the production of big modular metal heads, the metal-on-metal bearing should guarantee a low-wear result without osteolysis.

Between November 2000 and December 2003 45 patients requiring a revision were treated with a Birmingham Hip Resurfacing cup (MMT, UK) and a big metal-on-metal modular head. All surgery was done with a posterolateral approach. Cup sizes range from 44 to 66 mm, head sizes range from 38 to 58 mm. The head sizes most often used were 58 mm, 54 mm and 50 mm. All patients were prospective followed using the Orthowave software (CRDA France).

In this series of 45 revisions (mean age 56.17) with large modular heads we encountered 2 dislocations, which give us a dislocation rate of 4.4%. One of these dislocations became recurrent and was revised to a full-constrained acetabular component.

Our own dislocation rate in revision hip surgery is 13% (21/159) in the anterolateral approach. Dislocations using the posterolateral approach increased this percentage to 14.8% (21/141). Taking in account that 31% of the causes of revision were infection and recurrent dislocation, this trial demonstrates that large diameter ball heads give beside a better range of movement also a statistically proven reduction in the dislocation rate in revision hip surgery.

The difference in outcome after uncemented ceramic-on-ceramic total hip and metal-on-metal resurfacing is looked at in comparable patient groups. Theoretical advantages in resurfacing are less bone resection, normal femoral loading, avoidance of stress shielding and restoration of normal anatomy. In addition, reduced risk of dislocation, less leg lengthening and easier revision should convince us to perform metal-on-metal resurfacing. These advantages of resurfacing, the subjective “better feeling” and having a more “normal” joint is illustrated by objective proof with functional scores and activity.

The first 250 cases of 1067 (September 1998 –March 2004) performed Birmingham Hip resurfacings (MMT, UK) (follow up 2–5 years, mean age 49.54) were scored clinically and functionally. In the same period (July 1996 – September 2003) 164 ceramic-on-ceramic Ancafit total uncemented prostheses (Wright Medical, US) were implanted inthe same age and activity group as the resurfacings. The first group of 126 patients (follow up 2 – 6 years, mean age 46.76) was compared with the resurfacing group. All the data were collected intra operatively and postoperatively, mostly in a prospective way.

At the most recent follow-up there was a significant statistical difference in Harris Hip Scores (global and total), and activity function between the 2 types of pros-theses. Resurfacing scored a Harris Hip Total of 97.9 (ceramic THA 92.1). Of the resurfacing patients 60.71 had a strenuous activity (ceramic THA 30.43). Dislocation rate in resurfacing group was 0.4% (ceramic THA 3%).

The early clinical results in the group of metal-on-metal resurfacing are very satisfactory with Harris and PMA scores indicating early clinical success. The high percentage of strenuous activity in this young patient group satisfies the expectations of the resurfacing. The difference with a normal uncemented hip is stated with a better outcome in Harris Hip Scores and a better activity level.

Introduction: The purpose of this retrospective study is to compare long-term whole blood metal ion concentrations (Co, Cr, Ni, Mo) between two different metal-on-metal total hip arthroplasties and a metal-on-polyethylene control group, in relationship with physical activity.

Materials and methods: Between 1996 and 2000, different conventional prosthetic designs were implanted at our hospital. For this study, three groups were chosen according to the bearing surfaces used. Patients who had undergone other surgical interventions with implantation of potential sources of Cr/Co were excluded. Patients taking medication or dietary supplements containing Cr/Co were also excluded. In group 1, 17 patients with a 28 mm metal-on-metal bearing, type Metasul (Zimmer), were included. Group 2 comprised 11 patients with a 28 mm metal-on-metal bearing, type M2a (Biomet). The control group consisted of 9 patients with a 28 mm metal-on-polyethylene bearing in combination with a cemented CoCr stem. The three groups were demographically comparable. The postoperative clinical performance was evaluated using the Harris hip score and the Merle-dAubigne score. The activity level was measured using the Baecke questionnaire. Whole blood samples were taken in a standardized way and analysed by high resolution inductively coupled plasma mass spectrometer analysis.

Results: At an average follow-up of 4 years, the mean Harris Hip Score was 88.35 in group 1, 82.64 in group 2 and 90.89 in the control group. The mean Baecke Activity Score was 7.32 in group 1, 5.51 in group 2 and 6.49 in the control group. The mean Cr level was 0.27 in group 1, 0.63 in group 2 and 0.19 in the control group. The mean Co level was 0.63 in group 1, 1.06 in group 2 and 0.51 in the control group. The mean Ni level was 1.11 in group 1, 1.10 in group 2 and 1.31 in the control group. The mean Mo level was 0.65 in group 1, 0.77 in group 2 and 0.56 in the control group.

Conclusions: At a minimum follow-up of 4 years, no statistically significant differences were seen in clinical outcomes among the three groups. The only statistically significant difference in metal ion concentration among the three groups was observed for the Cr concentration between the M2a group and the metal-on-polyethylene group. There is also a positive correlation between the ion concentrations (Cr and Co) on the one hand and the activity level and Body Mass Index on the other.

Introduction The outcome of conventional treatment of isolated end-stage patello-femoral arthritis is unpredictable. Encouraging success rates have been documented in the literature with the use of patello-femoral arthroplasty. A prospective study was performed to review the early outcome of patello-femoral arthroplasties at St Vincent’s Private Hospital.

Methods The prospective study involved 32 patients over a period from 1999 to 2002. There were eight males and 24 females, with a mean age at surgery of 65 years. The mean follow up was 1.6 years (0.3 – 4 years). The patients were scored pre-operatively and at each post-operative visit using the Knee Society Score. Subjective results also recorded at follow-up included 1) the patient’s satisfaction in regard to pain and function, 2) whether expectations were met from the surgery and 3) if the patient would have the same operation on the other limb if the same symptoms existed. There were 31 knees available for post-operative analysis.

Results The mean knee score pre-operatively was 65.9 and post-operatively 84.3. The mean functional score pre-operatively was 75.7 and post-operatively 83.2. The mean pre-operative total knee score was 141.6 and improved to 167.5 post-operatively. The descriptive post operative Total Knee Score equates to 26 (83.9%) patients with excellent or good results and five (16.1%) patients with fair or poor results. Subjectively 87.2% of patients had an improvement in pain, 83.9% had an improvement in function, 80.7% had their expectations met and 77.5 % would consider the surgery again if required on the other leg.

Conclusions This review of the early experience of patello-femoral arthroplasty has shown patello-femoral arthroplasty to be a viable treatment option in the short term for end stage patello-femoral arthritis.