Tritanium Acetabular Cup in Revision Hip Replacement: A Six to Ten Years of Follow-Up Study.

BACKGROUND: The use of highly porous acetabular components has shown to produce good results in revision acetabular surgery. Their surface characteristics enhance initial fixation and bone ingrowth which are prerequisites for adequate osseointegration. The purpose of this study is to analyze the mid-term to long-term survival, clinical and radiological outcomes using the Tritanium cup (Stryker, Mahwah, NJ) in revision hip surgery. METHODS: This is a retrospective review of all patients who underwent acetabular revision surgery using "Tritanium revision cup" between April 2007 and November 2010 at our institution. Sixty-two patients were included with a mean age of 67.5 years (32-86). According to Paprosky classification, 10 patients had type I defect, 8 had type IIA, 27 had type IIB, 7 had type IIC, and 10 suffered from type IIIA defect. A Kaplan-Meier analysis was used to determine the survival of the cup. Functional outcomes were assessed using Oxford Hip Score. Plain radiographs were performed to assess implant fixation and osseointegration. RESULTS: The acetabular cup aseptic survivorship was 98.4% at a mean follow-up of 87.6 months. The mean Oxford Hip Score improved from 14.5 (3-31) preoperatively to 38.5 (12-48) at the final follow-up. Two cups were revised (3.2%): 1 for aseptic loosening and 1 for infection. CONCLUSION: Tritanium revision acetabular cup has shown excellent mid-term to long-term clinical and radiographic results with low failure rate and minimal complications. Longer term follow-up would be of value to assess the ongoing survival of this implant construct.

Midterm results with Birmingham Hip Resurfacing/Synergy stem modular metal-on-metal total hip arthroplasty.

Large head modular metal-on-metal total hip replacement (MoMTHR) has been shown to have increased revision rates in the National joint registry and in literature. We reviewed 41 consecutive patients with 44 hips who had large head MoM THR using a Birmingham Hip Resurfacing (BHR) cup/Synergy stem combination between June 2005 and Nov 2009 with a mean followup of 59.5 months. In this series we had a revision rate of 6.8% (3/44) for adverse reaction to metal debris (ARMD), persistent groin pain and instability. Kaplan-Meier analysis showed a mean cumulative survival rate of 79.2% (95% CI: 75.5%-82.9%) In addition there is a subset of 5/44 patients (113%) with mild grade groin pain who may need revision in the future. Based on these findings, we do not recommend performance of large head MoMTHR in the future.

Combined hip arthroscopy and limited open osteochondroplasty for anterior femoroacetabular impingement: early patient reported outcomes.

Many surgical techniques have been described for femoroacetabular impingement (FAI) surgery to help with improvement of pain and function in symptomatic patients. The aim of this study was to evaluate early patient reported outcomes and complications using combined hip arthroscopy and limited open osteochondroplasty technique. We retrospectively analysed 27 hips in 26 patients. Outcomes were assessed using the nonarthritic hip score (NAHS), UCLA score and Visual analogue scale (VAS) pain score. The average age of patients was 31.3 years and they were followed up for an average of 22.3 months. Average improvement of NAHS score was 39.55 points (p<.0001), 18 patients (72%) had at least 30 points increase in NAHS. There was 3 points average improvement in UCLA score (p<.0001). 17 patients (68%) had UCLA activity level of 6 and above. The average improvement of VAS pain score was 27.5 points (p<.0001). Minor complications included neuropraxia of the lateral femoral cutaneous nerve in three patients who recovered at three months with no sequelae, while one patient developed asymptomatic heterotopic ossification Brooker grade I. One patient had neuropraxia of the sciatic nerve which recovered completely within six months. One patient had a conversion to THR at 12 months. This is an effective technique to treat FAI for reducing pain and improving function at short term follow-up and has a low complication rate without appearing to have a significant learning curve. The failure rate can be reduced if proper case selection is done.

Injuries caused by brake pedal loading of the midfoot.

In a frontal car crash, the driver’s foot and ankle may be injured due to loading by the brake pedal. The driver of a vehicle often has time to initiate emergency braking before an impending collision, which places the forefoot or midfoot over the brake pedal. During the crash, the pedal may induce dorsiflexion and axial loading of the ankle due to forward motion of the occupant and rearward intrusion of the pedal relative to the vehicle. In order to investigate the injuries caused by pedal loading, impact tests were conducted on three cadaveric lower limbs. The limbs were braced at the knee, and a pedal positioned beneath the midfoot was driven towards the knee, inducing dorsiflexion and axial loading of the cadaveric limb. Ankle injury was generated in two specimens. Both injured limbs sustained a medial malleolar fracture, and one limb also suffered a talar neck fracture. These results suggest that pedal loading may be an important injury mechanism for fractures of the medial malleolus and talar neck in drivers involved in frontal crashes.

Medial approach for hindfoot arthrodesis with a valgus deformity.

BACKGROUND: Surgical correction of valgus deformity of the hindfoot has traditionally been via a lateral incision, often complicated by wound healing problems and sural nerve damage. Potential advantages of a medial approach especially for a valgus deformity include excellent wound healing, no risk of damage to the sural nerve and extensibility of the approach to include additional procedures such as navicular fusion or tendon transfer if indicated. MATERIALS AND METHODS: We present a retrospective review of 18 consecutive patients with valgus deformity of the hindfoot, all undergoing arthrodesis via a medial approach. Indications included osteoarthritis, tibialis posterior dysfucntion, post-traumatic arthritis and rheumatoid arthritis. RESULTS: All wounds healed by primary intention and there were no postoperative neurovascular complications. The mean preoperative subtalar valgus deformity was 32 (range, 12 to 49) degrees, which was improved to mean postoperative valgus deformity of 17 (range, 10 to 25) degrees. Fusion following the primary surgery was achieved in all but one of the patients (a heavy smoker and post-traumatic arthritis), with the mean time to fusion being 5.6 months. CONCLUSION: We provide further evidence to support previous documentation in the literature that the medial approach for the correction of hindfoot valgus deformity can be successfully used to achieve excellent exposure of the subtalar joint in order to correct the valgus deformity, avoiding the risks of wound healing and nerve damage associated with a lateral approach.

Snowboarder's talus fractures experimentally produced by eversion and dorsiflexion.

BACKGROUND: Fracture of the lateral process of the talus is an unusual injury that has received heightened attention in recent years because of its association with snowboarding. The diagnosis is often confused with that of lateral ankle sprain. If left untreated, it can cause long-term impairment, including osteoarthritis and subtalar joint degeneration. It is generally thought to result from dorsiflexion and inversion. However, few experimental studies have been conducted to investigate the injury mechanism. HYPOTHESIS: Eversion of a dorsiflexed ankle is more likely to fracture the lateral process of the talus than inversion of a dorsiflexed ankle. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric leg specimens were subjected to dynamic inversion or eversion of an axially loaded and dorsiflexed ankle. RESULTS: Inversion failed to produce any fractures in three injured specimens. However, all six specimens subjected to eversion sustained a fracture of the lateral process of the talus. CONCLUSIONS: The incidence of fracture of the lateral process of the talus was significantly higher in the eversion group compared with the inversion group. CLINICAL RELEVANCE: Eversion of an axially loaded and dorsiflexed ankle may be an important injury mechanism for fracture of the lateral process of the talus among snowboarders.

The effects of axial preload and dorsiflexion on the tolerance of the ankle/subtalar joint to dynamic inversion and eversion.

Forced inversion or eversion of the foot is considered a common mechanism of ankle injury in vehicle crashes. The objective of this study was to model empirically the injury tolerance of the human ankle/subtalar joint to dynamic inversion and eversion under three different loading conditions: neutral flexion with no axial preload, neutral flexion with 2 kN axial preload, and 30 degrees of dorsiflexion with 2 kN axial preload. 44 tests were conducted on cadaveric lower limbs, with injury occurring in 30 specimens. Common injuries included malleolar fractures, osteochondral fractures of the talus, fractures of the lateral process of the talus, and collateral ligament tears, depending on the loading configuration. The time of injury was determined either by the peak ankle moment or by a sudden drop in ankle moment that was accompanied by a burst of acoustic emission. Characteristic moment-angle curves to injury were generated for each loading configuration. Neutrally flexed ankles with no applied axial preload sustained injury at 21 +/- 5 Nm and 38 degrees +/- 8 degrees in inversion, and 47 +/- 21 Nm and 28 degrees +/- 4 degrees in eversion. For ankles tested in neutral flexion with 2 kN of axial preload, inversion failure occurred at 77 +/- 27 Nm and 40 degrees +/- 12 degrees , and eversion failure occurred at 142 +/- 100 Nm and 41 degrees +/- 14 degrees . Ankles dorsiflexed 30 degrees and axially preloaded to 2 kN sustained inversion injury at 62 +/- 31 Nm and 33 degrees +/- 4 degrees , and eversion injury at 140 +/- 53 Nm and 40 degrees +/- 6 degrees . Survival analyses were performed to generate injury risk curves in terms of joint moment and rotation angle.