Hip Resurfacing



Hip Resurfacing


Scott K. Siverling, PT, OCS

Edwin P. Su, MD


Dr. Su or an immediate family member serves as a paid consultant to Smith & Nephew; has stock or stock options held in Orthoalign; has received research or institutional support from Smith & Nephew; and serves as a board member, owner, officer, or committee member of the American Journal of Orthopedics and Techniques in Orthopedics. Neither Dr. Siverling nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.



Introduction

Hip resurfacing (HR) is a joint replacement procedure and alternative surgical option to total hip replacement (THA). HR allows conservation of bone in comparison to the traditional THA. Recent advancements in surgical technique, instrumentation, and prosthetic design of HR have improved the durability of HR prostheses and allowed increased motion and activity for those patients seeking surgical treatment of end-stage hip osteoarthritis (OA) when compared to contemporary posterior-approach THA.

The HR components involve a metal femoral cap with a short stem being inserted into the femoral head, once diseased and arthritic bone is eliminated surgically. Healthy bone of the femoral head and neck are preserved. The acetabular component is similar to the traditional THA acetabular prosthesis, utilizing the placement of a metal cup into the manually formed acetabular socket (Figure 37.1).

In addition to bone conservation, the appeal of HR is an increased postoperative activity level as compared to THA. Current thought and protocol regarding THA advises lower-level activity and a cessation of running and high-impact sports in order to preserve the prosthesis and avoid dislocation. The larger femoral component utilized in HR decreases the risk of dislocation and enables increased range of motion (ROM). The inherent stability and mobility of the HR prosthesis allows higher-level daily and recreational activity.

Guidelines for postoperative rehabilitation following HR have been proposed by the authors. The rehabilitation is divided into three phases. The first phase is considered the maximum protection phase, the second phase is the functional strengthening phase, and the third phase is the return to activity and/or sport phase. These guidelines are meant to assist in decision making for the practicing rehabilitation clinician in treating a patient who has undergone HR via the posterior approach. Other approaches, such as the anterolateral or anterior, may also be used and may require some modifications of the rehabilitation protocol, which should be discussed with the surgeon.






Figure 37.1 Radiograph of a hip resurfacing arthroplasty.


Indications

The ideal patient to undergo an HR is a male under the age of 65 years or a female under the age of 60 who has exhausted conservative care for a symptomatic arthritic hip joint.
Candidates must have normal bone stock, as determined by plain radiographs, in order to support the femoral cap and stem. Subjects with evidence of large or numerous cysts and pitting within the bone may be at a greater risk for postoperative fracture.


Contraindications

Contraindications to undergoing HR include females of childbearing age, severe obesity, renal insufficiency, and patients with known metal allergy or metal sensitivity. Osteoporosis may weaken existing bone, providing inadequate support, and may decrease the stability of the prosthetic components, increasing the risk of fracture.


Surgical Technique

The patient is positioned laterally for the posterior surgical approach, and the arthritic hip joint is exposed. For proper exposure and insertion of the acetabular component, a complete capsulotomy is necessary. The acetabular socket must be positioned ideally in order to avoid edge loading and erosion of the prosthesis. The socket is placed more horizontally, at approximately 40° of abduction, for protection against edge wearing.

The femoral head is sculpted, eliminating the diseased bone, and a metal cap with a short stem is placed into the underlying healthy bone. The femoral neck remains intact and is preserved. When aligning the femoral cap and stem, it is important to ignore the parameters of the femoral head—often, the femoral head is congenitally misshapen and can guide the surgeon toward improper femoral cap placement. The femoral component is instead inserted aligning to the center of the femoral neck.

Although a majority of the femoral head is retained during HR surgery, the preserved bone is briefly compromised by the surgical procedure. Excision of the arthritic bone and placement of the prosthetic cap and stem temporarily weakens the bone, increasing the risk of a postoperative fracture involving the femoral head or neck.

Metal ion dispersal into the bloodstream is a concern and risk following HR. To date, the authors have no knowledge of a predictive test for metal allergy or sensitivity. The current generation of metal-on-metal prostheses minimizes surface wear; however, metal ion dispersal has been observed in a small percentage of patients. Carrothers reported a 0.3% incidence of aseptic lymphocytic vascular and associated lesions (ALVAL) over a 5,000-subject sample. Those patients with normally functioning kidney and execratory systems are able to eliminate the cobalt and chromium metal ions through the urine. Metal ion blood levels are monitored on a regular basis following HR.

It is inferred that the increased exertion and activity of the younger demographic that have undergone HR may lead to a higher risk for heterotopic ossification (HO). The prophylactic use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) may be used to prevent ankylosing or severe HO.


Rehabilitation

Rehabilitation following HR surgery is divided into three basic phases. These phases have temporal properties, but the advancement between phases should be judged by the achievement of the milestones and goals outlined in each phase.

Entering into surgery, many patients suffering from end-stage hip OA complain of debilitating pain and exhibit compensatory gait patterns, a loss of hip joint motion in multiple directions, and muscle atrophy with weakness in the surrounding musculature. All of this can lead to altered neuromuscular patterns that may be suboptimal for efficient and pain-free movement. The correction of substitution patterns is emphasized during rehabilitation, and proper movement is instilled. Neuromuscular reeducation is imperative to achieve full recovery and to attain the patient’s goals.

Initially, ROM, healing, and advancement of independence with gait are the emphasis of the maximum protection phase. Strength of the specific muscles that control hip motion is the focus of the functional strengthening phase; however, ROM should not be neglected during the second phase. In the final phase, the clinician should focus on neuromuscular strengthening and sport-specific demands. While each phase emphasizes a different objective, each patient and his or her goals, physiologic deficits, and weaknesses vary. The clinician is reminded to individualize each rehabilitation program according to the deficits, inadequacies, and goals of the patient.


Maximum Protection Phase

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Oct 13, 2018 | Posted by in ORTHOPEDIC | Comments Off on Hip Resurfacing

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