Abstract
Modularity in total hip arthroplasty (THA) not only allows adjustments of leg length and offset but also simplifies the revision. It allows limited revision of various components and decreases surgical morbidity of complete revision. Despite benefits, modularity is associated with risks like corrosion and component dissociation. Dissociation between head and neck taper is rare and the cause is attributed to taper corrosion, revision, stem subsidence, pumping phenomenon, injury and closed reduction of dislocated THA. We report a case of late-onset impending head-neck dissociation in a THA caused by a well-fixed anteverted cup with polyethylene liner wear by “reverse bottle opener effect.” To our knowledge, this is the most late-onset reported case of head-neck dissociation, occurring after 13yrs of index surgery.
Keywords: Head neck dissociation, Total hip arthroplasty, Bottle opener effect, Impending, Spontaneous, Reverse bottle opener phenomenon
1. Introduction
Modularity in total hip arthroplasty (THA) reduces the morbidity of complete revision by allowing retention of well fixed component.1 But it is associated with risks like taper corrosion and head-neck dissociation (HND).1 HND is rare, commonly an acute event, attributed to taper corrosion, revision surgery, close reduction manoeuvre for dislocated THA, malunited fractures, impingement, ectopic ossification, prolonged immobility, stem subsidence or pumping phenomenon.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 The event could be as trivial as getting up from a chair or reaching out for an object (Table 1). Urish et al. documented two cases of impending HND where head was on the verge of dissociation due corrosive loss of neck taper.5 We are reporting a case of impending HND without corrosion, caused by “reverse bottle opener effect” (RBOE) created by a well-fixed anteverted acetabular cup and weight of limb (Video 1). To our knowledge this mechanism of dissociation has not been reported in the literature.
Table 1.
Review of literature on head neck dissociation following total hip arthroplasty.
| SN | Author | Duration∗ | Event∗∗ | Cause of dissociation |
|---|---|---|---|---|
| 1. | Karaismailoglu et al.2 | 3 years | rising from a sitting position | Ectopic ossification producing greater stress on head |
| 2. | Spinnickie & Goodman6 | 5 months | reaching out for an object while transferring from sitting in wheelchair | Polio with weakness, constrained liner, absent compression loading, distraction forces of flail lower extremity weight |
| 3. | Namba & Van der Reis7 | 1month | In bed | Constrained liner |
| 4. | Ahmed et al.8 | 5 years | rising from a chair | Sealed air pushes back the neck and unlocks the taper lock (pumping phenomenon) |
| 5. | Schuh et al.9 | 2 years | Non traumatic, use of wheel chair | Use crutches & wheelchair for several years leading to absent continual compression loading of the taper, impingement by acetabular reinforcement ring or heterotopic ossification. recurrent dislocations with several closed reductions |
| 6. | Regis et al.10 | 9 months | Flexion and slight adduction movement | Impingement of the base of the ball head against the lesser trochanter due to stem subsidence |
| 7. | Shiga et al.11 | 1month | While bathing | Impingement of stem neck and cup within the acetabulum when the hip was forced into flexion, adduction, and internal rotation causing failure of the taper locking mechanism; pumping phenomenon |
| 8. | Raviraj et al.12 | 1 year | minor abduction, outward twisting movement of leg | Lesser trochanter fracture with stem subsidence & relative shortening of neck; pull of psoas |
∗Duration fom last surgery (Index or revision).
∗∗Corrosion and closed reduction of dislocated total hip arthroplasty were excluded
Supplementary video related to this article can be found at https://doi.org/10.1016/j.jcot.2020.10.046.
The following is the supplementary data related to this article:
1.1. Case history
A 46 years old male, who had undergone uncemented THA (Zimmer, Indiana, USA) of left side 13 years (2005) back, presented with non-traumatic left hip pain for 6 months. Patient was not able to bear weight and was mobilizing with crutches. X-ray suggested an anteverted cup and an eccentric head in cup (Fig. 1). Blood markers were negative for infection and metal ions. MAVRIC magnetic resonance study suggested moderate effusion and peripheral synovial thickening (Fig. 2).
Fig. 1.
Preoperative Radiograph. (A) AP view; (B) anteverted cup on lateral view.
Fig. 2.
MAVRIC MR sequence showing moderate suppression of magnetic susceptibility artefact from total hip arthroplasty implant. (A) Coronal T1 image & (B) Coronal STIR fluid enhanced image reveals moderate hip effusion with hypo-intensity within the capsule (small solid arrow), associated fluid accumulation and erosion into greater trochanter (small arrowheads) and acetabular roof (asterisk), preserved marrow signal around the stem (hollow arrow) and cup (hollow arrowhead) without the evidence of loosening; (C) Axial fat-suppressed proton density-weighted image & (D) Axial STIR fluid enhancing MAVRIC image shows lobulated fluid collection (long arrow), susceptibility artefact is greatly reduced in (C) showing intermediate signal intensity with a low signal intensity at periphery suggestive of synovial thickening (large solid arrowhead).
During surgery, hypertrophic synovial tissue was observed with clear serous fluid. There were no signs of severe tissue damage (metallosis, pseudotumour, tissue necrosis) or infection (Fig. 3A). There was no corrosion at head-neck junction (Fig. 3). Indentations marks of impingement was evident between neck and cup margin as well as between head and liner (Fig. 3). The head (28mm, −3.5) sitting loosely on the neck taper, was easily removed but stem was well fixed. The neck taper and inside of the head displayed minimal fretting (Fig. 3). Liner wear created an oblong space with a well fixed excessively anteverted cup (Fig. 3H).
Fig. 3.
Intraoperative images and retrieved implant. (A) Showing synovial thickening with no evidence of corrosion or metallosis at head-neck interface; (B) after revision of the acetabular cup, liner and head. Note the decrease in visible length of neck trunnion (with 28mm + 0 head marked by black arrow) when compared to preoperative trunnion (with 28mm-3.5 head; marked by white arrow); (C) magnified image of neck showing impingement mark; (D) minimal fretting inside the head; (E) head showing markings by poly impingement (arrow head); (F) Exterior of head showing no signs of wear/corrosion; (G) Cup with poly showing poly wear and cup margin indentation (hollow arrow) caused by neck; (H) Poly liner showing wear.
We revised the cup (Trident PSL, Stryker, Michigan, USA), liner (MDM, Stryker) and head (28mm + 0, Zimmer, Indiana, USA) but retained the stem (Fig. 3, Fig. 4). Firm impaction of head was confirmed by manual pulling.
Fig. 4.
Hip Xrays. postoperative AP (A) and lateral (B) view showing retained stem and corrected cup version; (C) and (D) pre and postoperative neck length below the level of head. Neck length is smaller postoperatively with larger offset head.
Impending HND was documented by comparing the visible length of the neck taper with old head (28mm and −3.5 offset) in situ to that of with a new head (28mm and 0 offset) in situ (Fig. 3A and B); confirmed by retrospective analysis of pre and postoperative X-rays (Fig. 4C and D). Frozen section, culture and histopathology reports from intra-operative samples were negative for infection and necrosis.
Range of motion and strengthening exercises started on postoperative day one, however, weight-bearing delayed for 6 weeks. At 2 years follow up, the patient was pain-free, walking normally and there are no signs of implant failure.
2. Discussion
HND is a specific complication of modular THA.2 A strong blow on the head with a 0.5 kg mallet is adequate for desired head-neck impaction.3 Lieberman et al. showed that the average failure load for pull-off tests of the Zimmer prostheses was 4453 N ± 570 N (Cobalt alloy head and titanium stem).13 Impaction is maintained by cyclic loading during daily weight-bearing activities.9 Therefore, an acute strong distraction force or a distraction force for prolonged period between head and neck taper is necessary for disimpaction of head from neck.
Close reduction manoeuvre for dislocated THA can produce strong distraction force, where head is impinged against outer margin of cup (Bottle Opener Effect; BOE) causing HND.3,4 Lower distraction forces are needed in cases of corrosive trunnion loss where head loses the trunnion support.1,5,9 Impingement from ectopic ossification, excessive external rotation from abnormal anatomy and subsidence of stem also appears to produce strong distraction forces.1,2,7,9
Our review of the literature suggested that most HNDs occurred following trivial events indicating presence of distraction force at neck taper and mechanical block to the head over a prolonged period (Table 1). We excluded HND as a consequence of corrosion or reduction attempt of dislocated hip prosthesis from our search.
Spinnickie and Goodman reported a non-traumatic HND in a patient with poliomyelitis.6 Schuh et al. also reported a spontaneous HND case in a patient who had undergone multiple closed reductions for dislocation following which he was using crutches for years. Both papers attributed the complication to the lack of cyclic compression and pull from lower extremity weight.6,9
In our case also, compressive loading was absent and a strong pull-off force of lower limb was present for a prolonged period of time (Fig. 5). Polyethylene wear created an oblong space allowing movement of head up to cup margin, where excessively anteverted cup created an impingement point from inside. Non weight bearing ambulation produced a strong RBOE at this impingement point for months causing head to dissociate from the taper (Fig. 5, Video 1). However, the HND was incomplete; on the verge of complete HND and any trivial event like getting up from the chair would have resulted in complete HND.
Fig. 5.
Mechanism of dissociation by reverse bottle opener effect.
BOE from outer margin of the cup is well documented during attempts of close reduction of dislocated hip replacement.3, 4, 5 In our case report, mechanical block to the head from inner margin of the cup caused HND; hence the RBOE. We believe that any pathology; as described in literature; that can cause mechanical block to the head in combination with strong distraction force at neck can lead to HND by the virtue of RBOE. Therefore, biomechanical studies are warranted and meticulous case reporting needs to be done.
Cooper et al. published a study on 10 patients with head-neck taper corrosion treated with limited revision with good early outcome.3, 4, 5 Modularity helped us to spare the stem (Fig. 4). Clearly the benefits of modularity weigh more than risk of dissociation. THA patients with impingement symptoms are at high risk for dissociation and their imaging needs to be cautiously studied to avoid catastrophic outcomes.
In literature, maximum time interval between THA and HND reported was 10yrs, which makes our report, the most late HND (after 13 years of index surgery).3, 4, 5 Therefore, vulnerable patients need to be identified and followed up for longer duration.
In conclusion, nontraumatic HND is rare and possible without corrosion. Recognizing HND and diagnosing the cause is essential to prevent catastrophic failure and initiate appropriate treatment. The phenomenon of “Reverse Bottle Opener Effect” needs to be validated by reporting more cases and conducting in vitro studies. At risk population needs longer follow up and cautious imaging evaluation to avoid complications.
CRediT authorship contribution statement
Ramneek Mahajan: Operating surgeon, Investigation, Resources, Validation. Piyush Suresh Nashikkar: Conceptualization, Methodology, Formal analysis, Resources, Data c. Varun Khanna: Resources, Data c.
Declaration of competing interest
None.
Acknowledgement
Dr Anchit Uppal and Dr Akash Sabharwal gave valuable input during writing of the manuscript.
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