Treatment of Hip InstabilityTreatment of hip instability
Section snippets
Subluxation Versus Dislocation
Although the anatomic difference between dislocation and subluxation is clear, with loss of contact of the articular surfaces in the former, the clinical difference is less obvious. The generally accepted clinical definition is that dislocation requires an intervention to relocate the hip, whereas if with time or self-positioning the hip reduces, it is deemed to have subluxated. In subluxation, a clunk is heard or felt, and the hip feels unstable. This clunk usually, but not necessarily, is
Precipitating Event
Even the prosthesis that is orientated perfectly with optimal soft tissue tension can dislocate as a result of a fall or extreme movement; however, in most cases, there is no such precipitating traumatic episode.2, 6, 20, 55 Acute and chronic disorders of mental capacity frequently create difficulties with compliance in hip precautions in the early postoperative period. Woolson and Rahimtoola56 found that 13% (6 of 47) of patients with what they termed cerebral dysfunction suffered a
Examination
Assessment should be made of the patient's general condition and compliance with regard to any further possible surgery. The range of movement is determined, and if the hip is markedly mobile, marked stretching of the pseudocapsule should be considered. The general muscular control of the limb is assessed, with particular attention paid to any abductor deficiency. Leg-length discrepancy is noted; however, there is no clear correlation between overall leg length and stability.10, 55
Radiologic Assessment
Anteroposterior and lateral radiographs are obtained to determine the position, orientation, fixation, and wear of the components as well as the neck length and offset, the head-to-neck ratio, and the congruence of the reduction. The presence of any osteophyte or cement that might cause impingement and the condition of the greater trochanter are noted.
The acetabular orientation can be difficult to measure accurately on plain films, and various techniques are available to aid in its assessment.
Assessment of the Cause of Instability
Instability is multifactorial, and in most unstable hips, more than one potential reason for instability can be identified.11, 15, 16 A logical assessment of all possible primary and secondary causes is necessary, and Eftekhar16 suggested classification into 3 groups—mechanical, anatomic, and technical—on which Dorr et al15 have expanded (Table 1).
Type Empty Cell Single Multiple Reoperation Rate I. Positional 63% (10) 9% (2) 17% II. Soft tissue imbalance 25% (4)
Initial Management
The initial management of the dislocated hip arthroplasty is by closed reduction, under sedation, general anesthesia, or spinal anesthesia. Closed reduction was reported to be possible in 95% of 331 dislocations in Woo and Morrey's series55 and 64% (9 of 14) to 100% (11 of 11) of cases in smaller studies.4, 5, 20, 42 With the first dislocation, provided that the components are in an acceptable position after reduction, treatment is generally by a period of movement restriction. In 2 of 9 closed
Closed Reduction as a Definitive Treatment
Closed reduction of first dislocations, with or without subsequent movement restriction, generally has been reported to be successful in preventing further recurrence in 62% (48 of 77) to 80% (20 of 25) of hips.2, 9, 30, 50, 55 After reduction, either a period of guided mobilization or external constraint is advised, particularly with first-time dislocations. A half-leg hip spica cast in slight flexion and abduction, a hip brace, boot and bars or a Petrie cast, derotation boot, longitudinal
Open Reduction
Failure to gain a concentric reduction is usually because of interposed soft tissue or other material and warrants open reduction. The literature indicates that open reduction is necessary in 0 (0 of 11) to 36% (5 of 14) of cases,4, 5, 20, 25, 50, 55 although in some series the threshold to perform open reduction may have been decreased to facilitate early prosthetic revision. Grigoris et al25 described a case of iliopsoas tendon displacement behind the femoral neck after reduction of an early
Revision Arthroplasty
Most surgeons advise that if more than 2 dislocations have occurred, revision surgery should be considered, taking into account of the health of the patient and the patient's level of activity. Although different factors may be identified that theoretically could predispose to dislocation, when confronted with an unstable hip, the surgeon must determine which factors are likely to be causative and which if corrected would provide the desired stabilizing effect. Generally, the cause or causes of
Surgical Treatment Options
A wide variety of surgical procedures have been described to regain stability of the unstable THA, including revision of the femoral or acetabular components, cup augmentation or constraint, neck lengthening, increasing the head size, conversion to a hemiarthroplasty, removal of impingement, trochanteric reattachment or advancement, and other soft tissue procedures (Table 4).
Study Open Reduction Revision of Components Empty Cell
Final Outcome
The outcome of closed reduction of a first dislocation is success in 62% (48 of 77) to 80% (20 of 25) of cases.2, 9, 30, 50, 55 For the few that remain unstable and are suitable for revision surgery, the overall success of a first revision attempt was reported by Woo and Morrey55 as 69% (215 of 331 of hips.). If before reoperation there had been 3 or more dislocations, Daly and Morrey11 achieved successful stabilization in only 45% (17 of 38) of cases compared with 72% (41 of 57) if there had
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Cited by (45)
Inpatient Dislocation After Primary Total Hip Arthroplasty
2016, Journal of ArthroplastyCitation Excerpt :Dislocation is a common cause of patient dissatisfaction after THA that should be largely preventable with adequate patient education and monitoring, especially in the inpatient setting [25]. There is extensive evidence that procedural factors such as operative approach, soft tissue tension, component positioning, femoral head size, impingement, and acetabular liner profile affect dislocation risk [4-12,24], but little is known about the influence of nontechnical factors (eg, patient and hospital characteristics) on the likelihood of dislocation [26,27]. Preoperative identification of patients at increased risk of dislocation is important for developing targeted strategies to prevent this serious adverse event.
Dislocation Rates Following Primary Total Hip Arthroplasty Have Plateaued in the Medicare Population
2015, Journal of ArthroplastyHiL simulation in biomechanics: A new approach for testing total joint replacements
2012, Computer Methods and Programs in BiomedicineCitation Excerpt :As a consequence, the load-bearing capacity of the artificial joint is limited or not assured at all. As regards instability of total hip replacements (THRs), dislocation of the femoral head represents a major reason for revision procedures [1,2]. Mechanisms linked to subluxation and final dislocation of THRs involve impingement events where the femoral head is levered out of the cup due to prosthetic or bony contact [3].
Influences of head/neck ratio and femoral antetorsion on the safe-zone of operative acetabular orientations in total hip arthroplasty
2010, Chinese Journal of Traumatology - English EditionInfluence of femoral head size on impingement, dislocation and stress distribution in total hip replacement
2007, Medical Engineering and PhysicsHow Does Affect the Type of Instability after Total Hip Arthroplasty the Outcomes? Our Experience between 1999 and 2020
2023, Acta Chirurgiae Orthopaedicae et Traumatologiae Cechoslovaca
Address reprint requests to, Bassam A. Masri, MD, Department of Orthopaedics, Third Floor, 910 West Tenth Avenue, Vancouver, BC V5Z 4E3, Canada