What's new in hip arthroplasty

High short-term loosening rates with the Wagner Standard Cup

The stability of prosthetic fixation is to a large extent dependent on component design. The purpose of this study is to analyze the short-term radiological results obtained with the Wagner Standard Cup in primary hip arthroplasty. An assessment was made of one hundred primary hip arthroplasties. The radiological evaluation revealed bone ingrowth in 37 of cases, fibrous integration in 49 and loosening in 14. In summary, osseointegration of the Wagner Standard Cup was unsuccessful in a high percentage of cases. This finding, which was unrelated to the type of stem or bearing surface used, bore a statistically significant relation (P<0.05) with an observed poor bone coverage of the acetabular component. Although insufficient bone coverage could arguably be attributable to a poor surgical technique, we would tend to agree with other authors that it is rather likely to result from a flawed implant design that impedes osseointegration.

Revision total hip arthroplasty without bone graft of high-grade acetabular defects

Mixed results have been reported with bulk and cancellous bone graft to fill defects during acetabular revision arthroplasty. Jumbo cups have been used to maximize host bone contact, and if adequate initial stability can be achieved, this approach may provide a superior long-term outcome. We retrospectively reviewed a consecutive series of 107 acetabular revisions performed using jumbo cups without bone graft. Bone defects were assessed using a validated radiographic classification system that yielded 64 hips with significant bone defects for inclusion. Mean change in American Academy of Orthopaedic Surgeons lower extremity core and pain scores and in Short Form-12 scores showed increases of 22.01, 37.52, and 17.08 points, respectively. Postoperative radiographs consistently demonstrated host bone ingrowth into the jumbo acetabular shells, except for 3 failures. Careful incremental reaming up to a size that optimizes host bone support and contact may eliminate the need for bone graft in most acetabular revision arthroplasties.

Modular hybrid total hip arthroplasty. Experimental study in dogs

Background

This prospective experimental study evaluated the surgical procedure and results of modular hybrid total hip arthroplasty in dogs.

Methods

Ten skeletally mature healthy mongrel dogs with weights varying between 19 and 27 kg were used. Cemented modular femoral stems and uncemented porous-coated acetabular cups were employed. Clinical and radiographic evaluations were performed before surgery and at 30, 60, 90, 120, 180 and 360 days post-operation.

Results

Excellent weight bearing was noticed in the operated limb in seven dogs. Dislocation followed by loosening of the prosthesis was noticed in two dogs, which were therefore properly treated with a femoral head osteotomy. Femoral fracture occurred in one dog, which was promptly treated with full implant removal and femoral osteosynthesis.

Conclusions

The canine modular hybrid total hip arthroplasty provided excellent functionality of the operated limb.

Long-term results of the standard Wagner cup

Cementless acetabular components gained popularity because of the increased rate of loosening associated with cemented cups after intermediate and long-term follow-up. There are few long-term follow-up studies of cementless acetabular components. This study aims to evaluate the clinical and radiological long-term results of the press-fit standard Wagner Cup. Between January 1, 1994 and June 30, 1994, 118 implantations of a standard Wagner Cup were performed, and 102 implants were clinically and radiographically followed-up after a mean of 12.0 years. The Merle d'Aubigné score improved from a preoperative mean of 9.5 to 17.2 at latest follow-up. Early postoperative complications included two deep haematomata requiring needle aspiration, two deep vein thromboses, one pulmonary embolism, two temporary lesions of the sciatic nerve, one single event of THR dislocation and one recurrent dislocation. Two isolated cup revisions and five more complete total hip replacements were performed for aseptic loosening. The overall survival rate at 12 years was 93.1% (95/102). The standard Wagner cup yields very good long-term results.

Involvement of the lateral femoral cutaneous nerve as source of persistent pain after total hip arthroplasty

This report describes a situation in which the lateral femoral cutaneous (LFC) nerve was the source of incisional pain in a patient after a total hip arthroplasty. The painful scar was denervated by an approach that resected just the posterior branch of the LFC nerve. This was done through an incision near the anterior superior iliac crest, avoiding any potential exposure of the implant. One of the 3 patients reported here had a coexisting meralgia paresthetica that was treated by the same operative approach. The orthopedic surgeon should include the LFC nerve as an origin of persistent pain after total hip arthroplasty.

Survivorship of monoblock trabecular metal cups in primary THA : midterm results

Monoblock trabecular metal cups are made of a novel porous material intended to enhance ingrowth and improve fixation. We prospectively followed 223 consecutive patients with 245 trabecular metal acetabular cups implanted during primary total hip arthroplasties to determine the overall survivorship of the implant, and any association of survivorship to primary diagnosis and age, and to determine the fate of polar gaps and cysts. Minimum followup was 36 months (mean, 60 months; range, 36-112 months). Patients were assessed with the Harris Hip score and the Oxford questionnaire and radiographically with standardized serial radiographs. At last followup, all cups were radiographically stable with no evidence of migration or progressive radiolucencies. The survivorship with reoperation as the end point was estimated at 98.75% with a 95% confidence interval. Three reoperations occurred during the first 36 months. The Harris hip score increased from 48 to 94 and the Oxford score was 16.4 at the last examination. We observed no difference in terms of survivorship among patients with osteoarthritis, osteonecrosis, or hip dysplasia. Seven of 14 (50%) osteoarthritis cysts and 10 of 33 (33.3%) polar gaps detected on postoperative radiographs decreased or filled, whereas none of the remainder deteriorated with time. Our midterm results suggest this implant may enhance fixation, but long-term followup is needed to confirm our findings.

LEVEL OF EVIDENCE

Level IV Therapeutic study.

Pain and satisfaction after hip replacement: The patients perspective at 5 - 12 years

We present the results of a postal evaluation of 1700 hip replacements performed in 1560 patients at a specialist joint replacement centre. This 5 12 year follow-up assesses the patients perspective of satisfaction, pain levels, revision and dislocation rates, subjective issues related to the prosthetic hip and limitations to daily activities. Our adjusted response rate was 81.4%, with 89.2% of the respondents being satisfied with their hip replacement; 4.1% were dissatisfied, and 5.0% were unsure. 79% of patients reported no pain or slight pain, 14.5% had moderate pain and 2.6% had severe pain. 4.6% of the hip replacements had been revised, and 4.1% had dislocated. The hip was felt to be a limiting factor in their life by 18.4% of patients. The use of a questionnaire has provided long-term follow-up data at far less cost and considerably less inconvenience to the patient than a clinical review. We conclude that pain and patient satisfaction could be used as a simple screening tool for the vast majority of the patients. In those that have moderate or severe pain or express a lack of satisfaction for any reason, further clinical and radiological assessments could be carried out. (Hip International 2005; 15: 112-8).

Stellenwert der Endoprothetik im Bereich der Handchirurgie

Alloarthroplasty has largely replaced traditional procedures in arthrosis of hip and knee joints. In contrast the role of alloarthroplasty in comparison to traditional procedures in hand surgery has been uncertain. To evaluate this question every registered hand surgery department (n=307) in Germany received a questionnaire requesting information on number and type of implanted prostheses and traditional procedures concerning the wrist joint, distal radioulnar joint (DRUJ), first carpometacarpal joint (CMC), metacarpal phalangeal joint (MP), interphalangeal joint (PIP), and preferred characteristics of the prostheses. Of the 307 hand surgery departments, 150 (57% of the hospitals and 42% of the visiting surgeons) participated in the inquiry. Per year, only 98 wrist prostheses were implanted (distributed among five different models) but 1534 traditional procedures were performed. The Sauve-Kapandji procedure was the most popular for the DRUJ and was performed 264 times per year. In comparison 24 hemiarthroplasties were implanted at the DRUJ. Trapezectomy remains the standard procedure for arthrosis of the first CMC joint (n=1399). The future importance of alloarthroplasty of the CMC joint is doubted by the majority of participating hand surgeons (90.3%). In contrast the majority (85.3/71.8%) is convinced that alloarthroplasty will be of importance for the MCP and PIP joints, respectively. Currently, the number of implanted prostheses is close to the number of traditional procedures performed at the MP joint. Irrespective of the joint involved, cementless anchorage is preferred as is the surface replacement anatomical design. The results confirm that alloarthroplasty in hand surgery is of minor importance. Thus, the role of alloarthroplasty differs depending on the joint involved. Traditional procedures except for the MP joint continue to be of major importance in hand surgery.

Preoperative demand matching is a valid indicator of patient activity after total hip arthroplasty

The validity of preoperative demand matching as an indicator of patient activity following total hip arthroplasty (THA) was evaluated by studying 518 patients (mean age, 67 years; range, 26-92 years) who were assigned to 4 categories of decreasing demand: I (high demand), 68 patients (13%); II, 144 patients (28%); III, 281 patients (54%); and IV (low demand), 25 patients (5%). Preoperative Lahey Clinic Demand Category (as defined by age, weight, expected activity, health, and bone stock) was significantly correlated with self-reported, postoperative patient activity (P = .0038, R2 = .2024) and was much more predictive than any individual variable. Because patient activity is related to hip joint bearing surface wear, implant selection and resource allocation could be influenced by using demand matching to identify patients with high postoperative demand who may benefit from improvements in implant technology. Demand matching may also be used to stratify patient activity in long-term outcomes studies of THA.

Effect of the initial implant fitting on the predicted secondary stability of a cementless stem

A numerical model able to investigate the influence of biomechanical factors on the long-term secondary stability of implants would be extremely useful for the design of new cementless prosthetic devices. A purely biomechanical model of osseo-integration has been developed, formulated as a rule-based adaptation scheme. Due to its complexity, the problem was divided into three steps: preliminary implementation of the model (proof of concept); implementation of the complete model and investigation of the model solution; and model validation. The paper describes the first of these three steps. The model was implemented as a discrete-states machine, and the few parameters required were derived from the literature. It was then applied to a real clinical case. The study was conducted using the frictional contact finite element model of a human femur implanted with a cementless anatomical stem. A stable solution was achieved after between three and 15 iterations for all initial positions considered. Similar initial conditions yielded similar final configurations. The model predicted all initial configurations, with the exception of a partial osseo-integration, ranging between 62% (distal fit) and 78% (proximal fit) of the viable interface. This is in good agreement with the values reported in the literature that never exceed 75%, even in the best conditions, and report better clinical results for proximal fit. For the varus configuration, which lacks cortical support, the algorithm predicted a completed loosening.